According to the American Cancer Society, an estimated 1.4 million Americans were newly-diagnosed with cancer in 2004 and about 560,000 victims died from the disease. While medical advance have improved cancer survival rates, there is a continuing need for new and more effective treatment.
Cancer is characterized by uncontrolled cell reproduction. Mitosis is a stage in the cell cycle during which a series of complex events ensure the fidelity of chromosome separation into two daughter cells. Several current cancer therapies, including the taxanes and vinca alkaloids, act to inhibit the mitotic machinery. Mitotic progression is largely regulated by proteolysis and by phosphorylation events that are mediated by mitotic kinases. Aurora kinase family members (e.g., Aurora A, Aurora B, Aurora C) regulate mitotic progression through modulation of centrosome separation, spindle dynamics, spindle assembly checkpoint, chromosome alignment/segregation, and cytokinesis (Dutertre et al., Oncogene, 21: 6175 (2002); Berdnik et al., Curr. Biol., 12: 640 (2002)). Overexpression and/or amplification of Aurora kinases have been linked to oncogenesis in several tumor types including those of colon and breast (Warner et al., Mol. Cancer Ther., 2: 589 (2003); Bischoff et al., EMBO, 17: 3062 (1998); Sen et al., Cancer Res., 94: 1320 (2002)). Moreover, Aurora kinase inhibition in tumor cells results in mitotic arrest and apoptosis, suggesting that these kinases are important targets for cancer therapy (Manfredi et al., PNAS., 104: 4106 (2007); Ditchfield, J. Cell Biol., 161: 267 (2003); Harrington et al., Nature Med., 1 (2004)). Given the central role of mitosis in the progression of virtually all malignancies, inhibitors of the Aurora kinases are expected to have application across a broad range of human tumors.
CD20 (also known as Bp35) is a B-lymphocyte-restricted differentiation antigen that is expressed during early pre-B-cell development and remains until plasma cell differentiation. CD20 is a useful target for B-cell lymphomas as this antigen is expressed at very high densities on the surface of malignant B-cells, i.e., B-cells wherein unabated proliferation can lead to B-cell lymphomas. The Food and Drug Administration has approved the therapeutic use of an anti-CD20 antibody, rituximab (RITUXAN®), for use in relapsed and previously treated low-grade non-Hodgkin's lymphoma (NHL). Rituximab acts by binding to the CD20 antigen on B cells which results in the lysis of the B cell by a mechanism thought to involve complement-dependent cytotoxicity (CDC) and antibody-dependent cell mediated cytotoxicity (ADCC).
However, while anti-CD20 antibodies and, in particular, rituximab, have been reported to be effective for treatment of B-cell lymphomas, such as non-Hodgkin's lymphoma, the treated patients are often subject to disease relapse. Therefore, it would be beneficial if more effective treatment regimens could be developed. Combined treatment regimens could be helpful for patients suffering from B cell related tumors or other hematological malignancies, and might potentially even decrease the rate of relapse or overcome the resistance to a particular anticancer agent sometime seen in these patients. Additionally, combinations of anticancer agents may have additive, or even synergistic, therapeutic effects.
There is thus a need for new cancer treatment regimens, including combination therapies.